In general, a dialysis machine is used as a substitute for the natural kidney functions of a human body. As such, the dialysis machine cleans the blood of the natural accumulation of bodily wastes and excess fluid by separating the wastes from the blood outside the body or extracorporeally. The separated wastes are discharged and the cleansed blood is returned to the body.
A dialysis machine uses a dialyzer to separate the wastes and fluid from the blood. The dialyzer includes a porous medium located within an enclosure which separates the dialyzer into a blood compartment and a dialysate compartment. The blood removed from the patient flows through the blood compartment, and a prepared solution of dialysate flows through the dialysate compartment. The wastes and fluid from the blood pass through the medium by osmosis, ionic transfer or fluid transport into the dialysate, and depending upon the type of dialysis treatment, desirable components from the dialysate may pass in the opposite direction through the medium into the blood. The transfer of the wastes and fluid from the blood into the dialysate cleanses the blood while allowing the desired components from the dialysate to enter the bloodstream.
Accomplishing these functions requires a number of complex systems and components. In an extracorporeal flow path, which conducts blood from the patient to the dialyzer and then back to the patient, at least one arterial blood pump and optionally a venous blood pump move the blood and assist in performing certain types of dialysis treatments such as ultrafiltration. Peristaltic pumps are generally used as the arterial and venous blood pumps. Peristaltic pumps offer an advantage in that blood may be effectively transferred through the extracorporeal path without being contacted by a pump mechanism such as an impeller. A peristaltic pump includes a rotor which presses a flexible pump header or tubing against a stationary raceway. By pressing or pinching the flexible pump header against the stationary raceway, a quantity of blood is trapped and pushed in front of the rotor as it rotates along the stationary raceway.
Peristaltic pumps offer a number of advantages in dialysis machines. Since the flexible pump header confines the blood, the patient's blood is not required to come into contact with surfaces which are difficult or impossible to adequately clean and disinfect. Additionally, since the flexible pump header is a part of a disposable blood tubing set used in dialysis machines, and all of the patient's blood is confined to the dialyzer and the blood tubing set, sterilization is easily accomplished and effectively maintained throughout a dialysis procedure. Furthermore a peristaltic pump applies relatively gentle motion to the blood, as compared to the more vigorous motion of an impeller pump, and thus the potential to damage the blood is reduced with peristaltic pumps. Another advantage is that the quantity of blood flow through the pump depends primarily on the size of the pump header and the rotational rate of the pump rotor. Many other advantages of peristaltic pumps are known in the field of dialysis.
A disadvantage of peristaltic pumps is the difficulty of positioning the pump header between the rotor and the raceway before using the pump. The tolerances between the rotor and the raceway are sufficiently small to ensure that the pump header is pinched closed by the rotor pressure against the raceway. The close proximity of the rotor and raceway creates difficulties in fitting the pump header between the rotor and the raceway. Furthermore the position of the rotor and raceway relative to the remaining portion of the blood tubing set typically limits the space and accessibility for loading the pump header.
To alleviate some of the time consumed and difficulty involved in loading the pump header, a variety of mechanized loading devices have been incorporated in dialysis machines. One of the more complex loading mechanisms moves the rotor and the raceway axially with respect to one another to provide space for loading the pump header. The mechanism to accomplish such movements is somewhat difficult for the operator to use, has a complexity which increases the possibilities of mechanical failure or malfunction, and often does not provide adequate convenience and accessibility for the operator to insert the pump header.
Another approach previously used with dialysis machines to facilitate loading the pump header has been to move the raceway laterally away from the rotor. Although this provides additional space between the rotor and the raceway, there is frequently inadequate space for the operator to grip the pump header and stretch it over the rotor. Another approach used in the past has been to pivotably connect a portion of the raceway so the portion can be pivoted away from the rotor in a motion within a plane in which the rotor rotates. Pivoting only a portion of the raceway frequently does not provide sufficient space to constitute a material improvement in loading the pump header. Furthermore, many of the problems associated with the lateral movement of the entire raceway are also present when only a portion of the raceway is pivoted.
Most of the problems involved in loading the pump header or tubing are also replicated when the blood tubing set must be removed from the machine after treatment. An additional disadvantage of the prior mechanisms is that their complex structure and numerous parts makes cleaning them very difficult during the periodic cleaning of the dialysis machine.
It is with respect to the problems of loading the pump header or tubing of a blood tubing set on a peristaltic pump in a dialysis machine, and the relatively inadequate prior attempts to solve these problems, that this invention has evolved.